New research

Why measuring fugitive methane emissions from shale gas production matters

  • 24 Jul 2014, 14:40
  • Mat Hope

As an ever-increasing number of countries consider exploiting their shale gas resources, and researchers scramble to understand what a production boom could mean for the climate, two new pieces of research appear to come to opposite conclusions.

What is the climate impact of shale gas?

Since gas has about half the emissions of coal when it's burned for electricity, it has been touted as  a 'bridging fuel' for countries seeking to decarbonise their economies to use as a stop gap on the way to a low carbon electricity system.

But as we've  explored before, scientists are struggling to establish the full impact of increased shale gas production on the climate, due to methane that escapes during the extraction process - known as fugitive methane emissions.

Two papers released this month examine what the actual climate impact of natural gas is. At first glance they seem to show opposite things. The graph on the left, taken from a paper by Robert Howarth appears to show natural gas electricity generation emissions - the towering left bar - can be much higher than coal's. The second graph, from  Heath et al, appears to show the opposite - that coal's generation emissions (on the left) are much higher than those from both conventional and shale gas.

Howarth Vs Heath Coal And Gas Emissions

Both papers examine the 'lifecycle emissions' of the fuels: the amount of gas emitted from extraction to combustion. So why is there such a large discrepancy between two papers?

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Have satellites overestimated Antarctic sea ice growth?

  • 22 Jul 2014, 15:30
  • Roz Pidcock

It's puzzling why Antarctic sea ice seems to be growing while earth's other icy expanses are shrinking as temperatures rise.

Now new research questions whether there has been much of a rise in Antarctic sea ice after all. The paper suggests the small but significant growth scientists thought had occurred since 1979 could be little more than a "spurious artifact" of how satellite data is interpreted.

But other polar scientists tell us the implications of the new findings" are very limited indeed" and they're confident Antarctic sea ice is still growing.

Bucking the trend

Scientists know ice is being lost from both the Greenland and Antarctic ice sheets. They also know the amount of sea ice in the Arctic is rapidly decreasing.

But satellite data suggest the amount of sea ice around Antarctica has been growing since 1979. A report from the Intergovernmental Panel on Climate Change (IPCC) last year put the size of the increase at  1.5 per cent on average per decade.

For comparison, that's about a third of the rate of sea ice retreat in the Arctic. A  new paper just published in journal The Cryosphere explains the puzzle this poses for scientists:

"[T]here has been substantial interest in the trend in Antarctic sea ice extent … primarily because of the observed asymmetry between increasing ice extent in the Antarctic and rapidly diminishing ice extent in the Arctic, and the inability of current climate models to capture this."

The new paper raises an interesting point. It notes that the growth in Antarctic sea ice in the latest IPCC report is much bigger than suggested in the previous one in 2007. The authors say:

"[The 2007 report] reported the trend in Antarctic sea ice extent to be small and statistically indistinguishable from zero".

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Slow surface warming since 1998 is “not exceptional”, say scientists

  • 21 Jul 2014, 19:30
  • Roz Pidcock

Scientists know greenhouse gases are causing the world to warm. But an interesting question is why warming at earth's surface speeds up and slows down.

new paper shows surface temperature "slowdowns" like we're experiencing now aren't unusual - and capturing the timing of natural ups and down in the climate is key to predicting them.

But as a  second paper explains, the planet as a whole has warmed up in the last decade even as surface temperature rise has been sluggish.

Model mismatch

Temperatures are rising due to long term greenhouse gas warming. But natural variability causes temperatures to go up and down from one year to the next.

Natural variability can at least partly explain slower surface warming in the last 15 years, the Intergovernmental Panel on Climate Change (IPCC)  concluded in its latest report. Recent evidence  points to changes in the  Pacific causing the deep oceans to absorb more heat.

But most climate models didn't predict the slowdown. And as a  new paper in Nature Climate Change explains, some parts of the media have argued that since models don't replicate recent temperatures, we shouldn't trust their predictions for future warming.

But the paper, lead by Australian climate scientist Dr James Risbey, finds that 15 years of temperatures rising slower than models predict "does not constitute evidence against the fidelity" of models in general. Let's take a closer look at why not.

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